Androgen production by minced testis from adult rabbits was measured in response to a variety of FSHs and LHs from eutherian (sheep, rat, rabbit) and metatherian (kangaroo) mammals, a bird (turkey), reptiles (turtle, alligator) and an amphibian (frog). LHs from all three eutherian species were highly potent and produced clear stimulation at doses below 50 ng/ml; relative potencies in the rabbit were consistent with estimates from OAAD assay, but an anuran ovulation assay indicated considerable differences in potency among these three preparations. LH from the kangaroo had only about 4 percent the activity of the eutherian LHs in the rabbit testis. Potencies of mammalian (rat and ovine) FSHs were only a small fraction of the LHs (<1 percent); inactivation of ovine FSH by an LH-antiserum indicated that this low level of activity was due to residual LH contamination.